PRINTED CIRCUIT BOARD

Abstract

In a printed circuit board (1) comprising a plurality of insulating layers and conductive layers, and comprising at least one cavity (7) at least one electromagnetic coil (8) is arranged on an outer layer (4) of the printed circuit board (1) and cooperates with a permanent magnet (6) arranged inside the at least one cavity (7).

Claims

1. A printed circuit board (1) comprising: a plurality of insulating layers and conductive layers, and at least one cavity (7), wherein at least one electromagnetic coil (8) is arranged on an outer layer (4) of the printed circuit board (1) and cooperates with a permanent magnet (6) arranged inside the at least one cavity (7).

2. The printed circuit board of claim 1, wherein the cavity (7) is formed within an insulating layer (2) of a thickness of between 200 μm and 1000 μm.

3. The printed circuit board of claim 1, wherein the insulating layers (2) of the printed circuit board (1) are made from prepreg-material, in particular FR4-material.

4. The printed circuit board of claim 1, wherein the at least one electromagnetic coil (8) is a flat coil on an insulating layer (9) contacted to a conductive layer (11) arranged on the inside of the outer layer (4) of the printed circuit board (1).

5. The printed circuit board of claim 1, wherein the outer layer (4) of the printed circuit board (1) on which the at least one electromagnetic coil (8) is arranged is a layer of a membrane-material more flexible than the material of the insulating layers (2) of the printed circuit board (1).

6. The printed circuit board of claim 5, wherein the membrane-material is a flexible thermoplastic material.

7. The printed circuit board of claim 1, wherein the outer layer (4) is glued to the printed circuit board (1).

8. The printed circuit board of claim 1, wherein the outer layer (4) is fixed to the printed circuit board (1) by means of a layer of no-flow-prepreg.

9. The printed circuit board of claim 1, wherein the permanent magnet has at least one recess (7) to receive the at least one electromagnetic coil (8).

10. The printed circuit board of claim 1, wherein the permanent magnet has two recesses (7) to receive electromagnetic coils (8).

11. The printed circuit board of claim 5, wherein the membrane-material is selected from the group consisting of polyimide, polyethyleneterephthalate, polypropylennaphthalate, and liquid crystal polymer.

Description

[0018] The present invention in the following is described by way of an exemplary embodiment and with reference to the accompanying drawings in which

[0019] FIG. 1 shows a sectional side view of a printed circuit board according to the present invention,

[0020] FIGS. 2a) to 2b) show the production of a cavity within a semi-finished printed circuit board and the arrangement of a permanent magnet within the cavity, and

[0021] FIGS. 3a) to 3f) show the production of the outer layer carrying the electromagnetic coil.

[0022] In FIG. 1, the inventive printed circuit board is denoted by reference numeral 1 and it is basically comprised of a central insulating layer 2, a base layer 3 and an outer layer 4. The central insulating layer 2 comprises a cavity 5, in which a permanent magnet 6 is arranged. The permanent magnet has two recesses 7 to receive the electromagnetic coils 8, which are formed as flat coils etched out of a conductive layer that is arranged on an insulating layer 9. A line 10 contacts each coil to a conductive layer 11 arranged on the inside of the outer layer 4. The conductive layer 11 is appropriately patterned and connected to an electronic system (not shown) for processing the current pulses which result when the outer layer 4 vibrates in the direction of the double-arrow 12 in reaction to incoming sound. On the other hand, when the coil(s) 8 is (are) supplied with appropriate current, the outer layer 4 will vibrate accordingly thereby emitting sound. Hence, the inventive printed circuit board 1 has a built-in microphone/loudspeaker. The outer layer 4 is fixed to the central insulating layer 4 either by gluing or by means of a layer of no-flow-prepreg 13.

[0023] Referring now to FIG. 2a), the production of the inventive printed circuit board begins with the central insulating layer 2 and a base layer laminated to each other by techniques well known in the art of the production of printed circuit boards. A cavity 5 is provided within the central insulating layer 2 and a permanent magnet 6 fixed therein (FIG. 2b)).

[0024] The outer layer 4 with the electromagnetic coils 8 arranged thereon is produced starting from an outer layer 4, which can be a layer of polyimide having an appropriately patterned conductive layer 11 on one side thereof (FIG. 3a)). The arrangement of FIG. 3a) is covered with a release layer 14 (FIG. 3b)) which is well known in the art. In particular the release layer 14 preferably is formed by materials selected from the group comprised of metal soaps of Al, Mg, Ca, Na and Zn combined with a binding agent and a solvent. In the area of the release layer 14 firm adhesion of additional layers laminated onto the core material as depicted in FIG. 3c) will be prevented. As can be seen in FIG. 3c), it is proceeded to laminate a copper-clad laminate comprised of an insulating layer 9 and a conductive layer 8′. Subsequently, the electromagnetic coils 8 and the lines 10 for contacting them are produced by known techniques of photolithography and via-drilling (FIG. 3d). As can be seen in FIG. 3e), the copper clad laminate is cut and the regions of the insulating layer 9 not carrying the electromagnetic foils 8 are removed FIG. 3f). The element resulting from this procedure and depicted in FIG. 3f) forms the outer layer 4 on which the electromagnetic coils 8 are arranged and can be glued to the arrangement of FIG. 2b) or fixed by using no-flow-prepreg.